Unit 17—Ecology (& Populations) Ch. 30 Populations & Communities (sec. 1 & 4)

Populations, Communities, & Ecosystems (Sec. 1) What is a population? –All organisms of same type in the area What is a community? –All different organisms (populations) in the area What is an ecosystem? –All organisms & non-living (abiotic) factors in the area

Population Size & Arrangement How can populations be counted? –Animals Ear tags Leg bands Radio transmitters –Plants Marked w/ paint or ribbons What if a population is too large to count every individual? –Estimate using sampling techniques Count # in a small area, then multiply by total area mark & recapture Mark & Recapture Animation Mark & Recapture Game

Population Size & Arrangement How can a population distributed/ arranged in an area? –random –uniform –clumped What might be an advantage of a clumped population? What is population density? –# individuals/area Ex people/mile 2 What type of population distribution can be seen in the US? CT?

What can cause an increase in the population size of an area? –births –immigration What can cause a decrease in the population size of an area? –deaths –emigration Can you come up with an equation to show overall population change? –Population change = (B + I – D – E) or (B + I) – (D + E) Is population decreasing or increasing if change is: –positive? –negative? Population Changes

population pyramids (a.k.a. age structure diagrams) –basic shape can help us predict what’s going to happen to the population in the future… –What do you think will happen to the population in each pyramid??? Rapid Growth Guatemala Nigeria Saudi Arabia Negative Growth Germany Bulgaria Sweden Zero Growth Spain Austria Greece Slow Growth U. S. Australia Canada Ages 0-14Ages 45+Ages Visualizing Population Structures & Predicting Future Changes How Population Pyramids Are Made Video Animated Population Pyramid

Developing Countries –Wide base –High #s of pre- & reproductive age High birth rates –fast growth Developed Countries –slightly wider base, width is same, or inverted pyramid –lower #s of pre- & reproductive age –low birth rates slow growth, zero growth, negative growth (pop. shrinks) Population Pyramids (Age Structure Diagrams) Population growth rate by country

Population Clock

Population Growth Types of population growth: –exponential growth represents species’ biotic potential –ideal conditions –Logistic growth population reaches “carrying capacity” point of maximum growth Logistic Growth Exponential Growth

Population Growth Why don’t populations increase forever? –limiting factors provide environmental resistance prevent population from growing indefinitely –reach “carrying capacity” can be: –abiotic (non-living) –biotic (living)

Examples of Abiotic Limiting Factors

Organisms have a “range of tolerance” for abiotic factors –Thrive under some conditions (optimal range) –Survive, but are not well (stress zone) –Can’t survive (zone of intolerance) Abiotic Limiting Factors

Is temperature a limiting factor for these fish species? –Why/why not? Abiotic Limiting Factors optimal temperature

Examples of Biotic Limiting Factors Living factors in an ecosystem

Decomposers are heterotrophs Break down dead material & recycle nutrients Biotic Limiting Factors Usually described in terms of interactions –especially who eats whom or trophic levels

Other Relationships in a Community symbiosis –when 2 species live closely together in a relationship over time

Other Relationships in a Community: Commensalism One partner benefits from the relationship & the other neither benefits, nor is harmed

Other Relationships in a Community: Mutualism Both partners benefit from the relationship.

Other Relationships in a Community: Parasitism One partner benefits (parasite), & the other is harmed (host)

Other Relationships in a Community: Predation One organism benefits (predator), the other is harmed (prey)